1. Field of the Invention
The present invention relates to vehicle suspension systems, and more particularly, to a suspension system with a dynamic damper for reducing resonance noises generated mainly in a rear seat while a vehicle travels on bumpy roads.
2. Background Art
For example, when a two-box type vehicle travels on a bumpy road, xe2x80x9choot noisesxe2x80x9d belonging to a medium frequency band ranging from 310 to 370 Hz or xe2x80x9croaring noisesxe2x80x9d belonging to a low frequency band ranging from 160 to 190 Hz, may be generated from a rear seat or thereabout of the vehicle.
Investigations into sources of those noises have revealed that the noises of the medium frequency band is originated mainly from a strut of a rear suspension system resonated in the widthwise direction of the vehicle by a road surface input of 340 Hz or thereabout and the noises of the low frequency band is originated mainly from the strut resonated in the vertical direction by a road surface input of 180 Hz or thereabout.
In order to reduce the amplitude of such resonance vibrations, leading to the reduction of noises, it is an effective means to attach a dynamic damper composed of a spring-mass system to a suspension system to cause a resonance in the dynamic damper. As such an example of reducing the resonance amplitudes of the strut by means of the dynamic damper, there is a technique disclosed by Japanese Patent Application Laid-open No. Toku-Kai-Shou 63-97413.
This background technique is for reducing shimmy and includes a dynamic damper provided at the lower part of a strut of the front suspension system. The dynamic damper comprises a ring-shaped mass member, an intermediate sleeve rigidly fitted over the strut and two rubber elastic bodies provided opposite to each other for bonding these to the strut by vulcanization.
However, according to this technique, when this construction is applied to a rear suspension system, since the dynamic damper is mounted at the lower part of the strut in such a manner that it projects from the outer periphery of the strut, the dynamic damper has a possibility that it interferes with a wheel or a wheel apron depending on the arrangement of surrounding components, this resulting in an up-sizing of the wheel apron. Further, the dynamic damper has a fear that it is scratched by stones sent flying by a tire or splashed mud.
It is an object of the present invention to provide a suspension system capable of effectively reducing noises in the medium frequency band and more preferably in the low frequency band in the rear seat and whose component members are free from the fear of interference with other body component members.
To attain the object, a dynamic damper is provided with a strut of the suspension system. The dynamic damper is disposed between an upper spring seat and a strut mount and comprises a supporting plate secured to a piston rod of the strut and an annular inertia mass body mounted on the supporting plate through an elastic member. The annular inertia mass body is connected at two edge portions thereof located opposite to each other across the diameter with the supporting plate by a bolt and nut through the elastic member, respectively.